A Study of the Quality of Japanese Papers Used in
Conservation

Sue Beauman Murphy is Assistant Paper Conservator in the
conservation department of the Harry Ransom Humanities Research
Center, The University of Texas, Austin, Texas, 78713-7219.
Siegfried Rempel, formerly Conservation Scientist in Photography at
the Harry Ransom Humanities Research Center when this study was
conducted, is now with the Centre Canadien d'Architecture , 1440
ouest rue Saint-Catherine, 2eme etage, Montreal, Quebec, H3G IR8,
Canada.

The first phase of a project to determine the quality of Japanese
papers used in conservation treatments has recently been completed.
Over a year ago four major U.S. distributors of Japanese papers were
contacted: Aiko's Art Materials Import Incorporated,
Andrews/Nelson/Whitehead, Light Impressions Corporation, and
University Products Incorporated. The companies sent samples of
paper they considered conservation quality Japanese papers which
were currently available. From those samples, forty-nine papers were
selected for examination. Papers were selected on the basis of
descriptions provided by the distributors which promoted them as
conservation products. In addition, twenty-one handmade and fourteen
machine-made papers distributed through a Tokyo-based company, Paper
Nao, were added to bring the total number tested to eighty-four. The
first phase involved two analyses: pH cold water extraction and
fiber content.

Testing: pH Extraction

Three cold water extraction pH tests were run on each paper
according to TAPPI test T-509 om-83.1 The results of those three tests were then
averaged to obtain the final figures in Table
1.

The pH measurements indicate that all but a single paper fall in
the neutral or alkaline range, depending on the addition of alkalis
during preparation and cooking or from additions of calcium
carbonate as a buffer. It is reasonable to assume, however, that
those papers containing lignified debris or untreated wood fibers
will not remain stable, probably increasing in acidity over time.

Testing: Fiber Analysis

Examination of the fiber quality was carried out according to
TAPPI standard T-401 om-82. Specimens were torn into tiny pieces
from different areas of the paper sample, placed in a small beaker,
covered with dilute solutions of an alkali2 followed by an acid3, heating and rinsing well after each
chemical treatment. After the water was drained off, the pieces of
paper were rolled into a ball between the fingers and placed in a
test tube. Distilled water was added, and the contents were shaken
until the fibers were thoroughly dispersed. The fibers were
transferred to microscope slides using a disposable pipette. The
slides were dried on a warming tray, stained with Graff's C-stain,
and viewed through a Leitz triocular compound microscope using
transmitted light.

Fibers were identified on the basis of their morphological
characteristics and associated cellular matter, as well as their
color when stained. When necessary, measurements were taken of fiber
widths and associated cellular elements to aid in identification.
When more than one fiber type was identified on a slide, a count was
taken and the fiber ratios were tabulated according to weight
factors of those specific fiber groups.

With the benefit of a camera which attaches to the third ocular,
the paper fibers were photographed. All photomicrographs were taken
with Kodak Ektachrome Tungsten 160 ASA slide film at a magnification
of 250x. The results of the fiber analysis can be seen in Table 2.

Analysis of Data

Permanence and durability of a paper are of course directly
related to the processing and treatment the fibers receive during
the pulping process.4 In Japanese
papermaking, the Japanese fibers are cooked using one of at least
four alkalis , which helps, to a degree, to get rid of the acids
produced by lignin. However, with the use of Western wood pulp in
Japanese papermaking, a new variable has been added to the quality
of these papers. Naturally, the addition of any untreated wood
products to a paper, even in small amounts, will affect its
permanence and, in consequence, its durability. Of the papers
tested, a total of four samples (3.4%) contained untreated wood
fiber.

Another variable was found in the 100% kozo papers: associated
lignified shive material. Of eighty-four papers tested, fifty-five
papers (65.5%) were 100% bast fiber, and forty of the bast papers
(72.7%) were 100% kozo. During analysis, it was noted that kozo
fibers were often accompanied by associated lignified debris. The
photomicrograph in Figure 1 illustrates a 100%
kozo paper with very little residual shive material, whereas the
100% kozo paper seen in Figure 2 has a large
amount of lignified debris still present. This lignified shive
material occurs naturally in vascular plants, and is found under the
bark in kozo plants. The fibers are surrounded by it. The lack of
lignified material and debris in a kozo paper is an indication of
the efficiency of both the beating and cooking processes. It is
reasonable to assume the occurrence of residual lignified debris
will effect the permanence of a paper.

Fig. 1

Fig. 2

Fourteen (25.5%) of the bast fiber paper group were of gampi or
mitsumata. Under the microscope, it is quite difficult to
differentiate between gampi and mitsumata fibers, even with stain. A
simple test using sodium hydroxide was done to differentiate between
the two types of fibers in every case. The results of a positive
test for mitsumata can be seen in Figure
3.6 In no case did there appear
to be a paper containing a combination of gampi and mitsumata. Also,
in only one case, a paper called Kitakata Buff distributed through
Light Impressions, was there found any additions of wood fibers to
gampi or mitsumata, and then only 5% treated softwood was found.

Of all papers studied, only one paper consisted of 100% mixed
bast fibers. Uda Thin, distributed by Andrews/Nelson/Whitehead, was
found to contain 95% kozo and 5% of what appeared to be ramie, with
an occasional contamination of a gampi fiber.

Two of the eighty-four papers were 100% leaf fibers. These two
papers were L-Tissues made from manila hemp and distributed through
Andrews/Nelson/Whitehead and University Products.

Some interesting fibers were found in three of the machine-made
papers from Paper Nao. The papers were found to be about 75% bast
with 25% grass. The grass fibers were, however, very unusual, as
seen in the photomicrograph in Figure 4. Most
straw and grass fibers are accompanied by a wide array of cellular
debris, and the grass fibers found in the papers from Paper Nao were
no exception. There were, however, quite unusual paraphernalia, such
as several star-shaped cells and epidural cells with a very
characteristic cupped shape. Many of the fibers occurred in bundles
resembling ears of corn or sea anemone. At first, because of the
wide variety of fiber widths, combinations of different kinds of
fibers were considered. Some of the fibers were so thin the only
possibility appeared to be pineapple, a leaf fiber. From the
associated cellular matter, though, it was evident that grass or
straw fibers were present. Some of the associated debris was similar
to that found in bamboo, considered a grass, and since there are
hundreds of species of bamboo plants, it was felt the unusual
cellular matter might be from some obscure species of that genus. It
was finally decided that the fibers should simply be labeled as
grass fibers, and that the Paper Nao representative should be
contacted for further information. The Paper Nao representative
identified the "mystery fibers" as a form of Chinese miscanthus
grass called ryususo.

Fig. 3

Fig. 4

Today, because of the high cost of Japanese bast fiber, many
papermakers have added wood fiber to their stock. Of the eighty-four
papers tested, twenty-three papers (27.4%) had wood fiber added.
Nineteen of those twenty-three papers (82.6%) contained treated
soft- and/or hardwoods. One particular type of softwood found was
Douglas fir with its very characteristic striated spiral morphology.
It is important to differentiate between Douglas fir and other
softwood fibers because it has a higher weighting factor than most
fibers.7

Some of the papers tested were found to contain small amounts of
untreated processed wood fibers. Of the twenty-three papers found to
contain wood fibers, four (17.4%) contained anywhere from 5-30%
untreated softwood fibers.

It is interesting to note that there were three samples of
Mulberry Paper tested, with varying fiber furnish. This is curious
since one importer/distributor, Andrews/Nelson/Whitehead, sells to
the other two distributors. It seems logical those three
distributors would be selling the same paper. Yet the sample sent by
one company tested out to have 20% untreated softwood. Another
company sent a sample that proved to include 30% untreated softwood.
These papers are similar. In fact, given the potential of +/- 5%
margin of error in tabulation, they could be identical papers. The
surprise is the fiber composition of the third paper, distributed by
Andrews/Nelson/Whitehead, which appears to be made of 75% kozo and
25% softwood, with no untreated softwood.

There are a few inconsistencies of this sort, but none quite so
extreme. It seems likely one is dealing with inconsistencies in the
product from a particular supplier or a change to another supplier.

Summary and Conclusion

The Japanese papers examined in this study were found to be
generally of good quality, based on fiber composition and initial pH
readings. Fiber furnish is usually high-quality in traditional
Japanese papermaking, since papermakers in that country are using
primarily bast fibers. There are two factors, however, which do
effect the quality of these papers: residual lignified shive
material from partial processing and the addition of wood fiber as
an extender. The amount of additional wood fiber, as well as whether
it is treated, is easily quantified. Additions of wood fiber, even
if treated, will surely effect the durability of a paper, and if
untreated wood fiber is added, both permanence and durability are
effected. More difficult to determine is the amount of the residual
lignified product and the implications of its presence.
Nevertheless, it seems clear that there is an inconsistency in the
production of some of the papers which accounts for the unevenness
in quality. For this reason, it is important to perform continued
reviews of the quality of these papers. It will also be of interest
to research the implications of these variables through artificial
aging, followed by mechanical endurance tests. Quality checks such
as this may raise the consciousness of the conservation community,
in turn pressuring suppliers to produce products of unvarying high
quality. Continued monitoring of these papers will help simplify the
choice of products in the increasingly confusing market of
conservation supplies.

Table 1. Japanese Papers Ranked By Fiber
Quality

This ranking of papers by fiber content is based on the
understanding that Japanese paper making fibers are the ideal
papermaking fibers for this application and that non-traditional
fibers or partially processed fibers are less desirable as
components in the finished paper product.

Notes

1. noted by Browning, "The choice of extraction
procedure depends on expected interpretation of the pH values found"
(B. L. Browning, Analysis of Paper, [Appleton,
Wisconsin: The Institute of Paper Chemistry, 19771, 170-1).
According to Barrow, "When the rate of aging is judged by the rate
of decrease in folding endurance, the cold extraction method gives
higher pH values if the pH is below 7 ... [otherwise] the hot and
cold extraction methods may be expected to give about the same
values" (W. J. Barrow, "Hot vs. Cold Extraction Methods for Making a
pH Determination," TAPPI, vol. 46, no. 8 [August 1963]:
468). Further tests on the Japanese papers may include fold
endurance testing. Since cold water extraction is generally accepted
in paper conservation for product testing, it seemed logical for the
purposes of this study, therefore, to rely on cold water extraction
as the means for obtaining the most accurate pH readings.

2. 0.5% sodium hydroxide

3. 0.5% hydrochloric acid

4. Processing refers simply
to the cooking and beating part of the pulping process. It can infer
chemical as well as mechanical preparation. According to McGovern,
"Chemical pulping has as its purpose the selective removal of the
fiber-bonding lignin to a varying degree with a minimum solution of
the hemicelluloses and the celluloses" (J. N. McGovern,
"Introduction to Pulping," Pulp and Paper: Chemistry and
Chemical Technology, ed. by James P. Casey [New York: John
Wiley & Sons, 1980), 1:161). Further purification can be
continued in a bleaching step. For the purposes of this study,
"treated" refers specifically to chemical treatment using bleach to
remove the remaining lignin and lignified products both within the
fibers and in the surrounding associated material. Therefore, to
assure permanence, whenever wood products are used in paper
fabrication, it is necessary to treat those fibers.

5. As explained by Barrett,
the four major processes use calcium hydroxide (lime mortar), sodium
hydroxide (caustic soda), sodium carbonate (soda ash), and wood ash
(Timothy Barrett, Japanese Papermaking [New York:
Weatherhill, 19831, 145-9). The use of calcium hydroxide is
sometimes desirable as it can alkalinize the sheet to some degree.
An information list sent out from Paper Nao included the cooking
process used for each paper.

6.When a stained slide
appeared to have either gampi or mitsumata fibers, a second chemical
test was conducted on another slide using a drop of a 17.5% solution
of sodium hydroxide. When the clear alkaline solution is added to
gampi fibers, there is no response. However, when the solution is
added to mitsumata, intermittent bulging and swelling occurs.

7. Most softwood fibers have
a weight factor of 0.90. Douglas fir has a weight factor of 1.50.
TAPPI method T-401 om-82 discusses the precision required in
selection of proper weight factors. First demonstrated by Spence and
Krauss (G. K. Spence and J. M. Krauss, Paper, vol. 20,
no. 11 [May 19171:11-13), weighting factors were perfected by
several researchers, especially J. H. Graff whose publications have
been noted by Isenberg (I. H. Isenberg, Pulp and Paper
Microscopy [Appleton, Wisconsin: The Institute of Paper
Chemistry, 19671). The table of weighting factors used in this study
is taken from Isenberg.